A check valve (3) can prevent the natural chemical absorptionwater head of the water head when the manual pump or the mechanical pump stops to work.
止回阀(3)起当手压或机械泵停止工作时能阻止水位差的自然吸药。
2
ASTM D570 Standard Test Method for WaterAbsorption of Plastics scope:this test method covers the detetmination of the relative rate of absorptionwater by plastics when immersed.